Macitentan

What is macitentan?

Macitentan (brand name: Opsumit) is a medicine used to treat a condition called pulmonary arterial hypertension (PAH). This is a condition where there is increased pressure in the arteries that carry blood from the heart to the lungs.
PAH can occur in a number of rheumatological diseases such as scleroderma. These diseases can cause thickening of the blood vessel walls. Symptoms include shortness of breath during routine activity (such as climbing stairs), tiredness and chest pain.

How does it work?

Macitentan helps lower blood pressure in the lungs by opening up the lung blood vessels. This helps your heart pump blood through the blood vessels in the lungs more efficiently.

What benefit can you expect from your treatment and how is it monitored?

Macitentan can reduce the symptoms of PAH and in some cases prolong life expectancy. It may take up to 2 months or more before your symptoms start to improve.

Before macitentan can be prescribed, a specialist will assess you. This may be a rheumatologist, immunologist, cardiologist (heart) or a respiratory (lung) physician who has experience in managing PAH.
You will be asked to have the following tests:
• an ultrasound scan of your heart (echocardiogram)
• a right heart catheter – this is a test to measure the blood pressure in your heart and lungs. It involves inserting a tube into your heart from an artery in your neck, arm or groin.
• a six-minute walk test (6MWT) to measure how far you can walk in six minutes.

Every six months you will be asked to have the echocardiogram and the 6MWT to check that macitentan is still helping your condition.

How is macitentan taken?

Macitentan is a 10mg tablet. Macitentan should be swallowed whole with or without food.

What is the dosage and when should it be taken?

The normal dose is 10mg once a day.
Macitentan should be taken at the same time each day. It is usually taken in the morning or at night. If you forget to take a tablet you can take it later in the day. If it is the next day, take the normal dose (do not take a double dose).

Can other medicines be taken with macitentan?

Macitentan may be taken in combination with other medicines, including:
• steroid medicines such as prednisolone
• anti-inflammatory medicines (NSAIDs) such as naproxen (Naprosyn) or ibuprofen (Brufen/Nurofen) provided your kidney and heart function are normal
• pain-relieving medicines such as paracetamol and combined medicines such as Panadeine and Panadeine Forte
• calcium channel blockers (for Raynaud’s disease)
• diuretics (fluid tablets)
• warfarin (blood-thinning medicine)
• other treatments for PAH.
There are a number of medicines that should not be taken when you are taking macitentan.

How long is the treatment continued?

Macitentan may be given on a long-term basis provided it does not cause problems and continues to help your condition. It is usually given for as long as the 6-monthly tests (echocardiogram and 6MWT) show that it is of benefit.
Do not stop taking macitentan without first talking to your doctor. If your doctor decides to stop the treatment, you may need to reduce the dose gradually before you stop the medicine completely.

Are there any side effects?

Most people who take macitentan do not experience side effects. Tell your doctor if you are worried about possible side effects. Having a lower dose may reduce side effects so that you can continue taking macitentan.

Most common possible side effects
• The most common side effects include stomach upset, nausea, diarrhea and headache.
• Other side effects include inflamed throatand/or airways, irritated nose passages or skin rash.
• Runny or blocked nose, fever, flu, upper and lower respiratory tract infection or sinus infection.
• Dizziness due to low blood pressure, flushing, ankle and/or leg swelling can occur.
• Irregular heartbeats or tiredness have been reported.
• Low haemoglobin (anaemia) or low platelet counts can be detected on blood tests but rarely causes symptoms.

Less common or rare possible side effects
• Macitentan can cause severe liver problems. Symptoms include nausea, stomach pain, low-grade fever, loss of appetite, dark urine, clay-coloured stools and jaundice (yellowing of the skin or eyes). Call your doctor at once if you have any of these symptoms.
• There are also a number of other rare side effects.

What precautions are necessary?

Blood tests
• Your liver function and blood counts for haemoglobin will need to be tested before you start taking macitentan, and again each month during your treatment.

Use with other medicines
• Macitentan can interact with other medicines. You should tell your doctor (including your GP, rheumatologist and other health professionals) about all medicines you are taking or plan to take. This includes over-the-counter or herbal/naturopathic medicines.
• The following medicines may interfere with macitentan (note, this is not a complete list).
Some should not be taken with macitentan.
For others, the dose may need to be adjusted.
− cyclosporin (Cicloral, Neoral, Sandimmune)
− some antibiotics such as ciprofloxacin
− cholesterol lowering medicines
− anti-fungal medicines
− some drugs used to treat epilepsy
− HIV/AIDS medicines lopinavir or ritonavir (Kaletra, Norvir)
− tacrolimus (used to prevent rejection of liver or kidney transplants)
− rifampicin (used for tuberculosis).

Vaccines
• Most vaccines can be given safely with macitentan. Pneumovax, COVID and yearly flu vaccinations are safe and recommended to reduce your risk of those infections. Talk with your rheumatologist before receivingany vaccines.

Pregnancy, breastfeeding and male fertility
• Macitentan should not be taken during pregnancy or when breastfeeding.
• If you are a woman of childbearing age, you should use effective contraception while taking macitentan.
• If you are planning a family or you become pregnant during your treatment, you should discuss this with your doctor as soon as possible.
• If you are a male, taking macitentan may lower your sperm count. Talk to your doctor if you have concerns.

How to store macitentan

• Store macitentan at room temperature, away from heat, moisture and light (e.g. not in the bathroom).
• Keep all medicines out of reach of children.

Important things to remember

• While taking macitentan you should see your treating specialist regularly to make sure the treatment is working, and to minimise any possible side effects.
• Macitentan should be taken at the same time each day.
• You should not stop your treatment unless your doctor tells you to.
• You should not increase or reduce the dose of macitentan unless your doctor tells you to.
• Contact your doctor at once if you experience symptoms such as nausea, stomach pain, fever, loss of appetite, dark urine, clay-coloured stools or jaundice
(yellowing of the skin or eyes).
• Macitentan interacts with many other drugs.
Discuss with your doctor whether you need to change the doses of these drugs or avoid using them together with macitentan.

For more information see the Macitentan – printable information sheet.